Microsoft Corp. is using a $2 billion loan to help finance Dell Inc.’s $24.4 billion buyout to bolster one of the largest makers of computers using Windows software and fend off competition from Google Inc. and Apple Inc.. Steve Ballmer, Microsoft’s chief executive officer, discussed the loan with Dell founder and CEO Michael Dell, according to two people familiar with the negotiations. Microsoft opted for a loan rather than an equity investment to avoid rankling other personal-computer makers that use Windows, said one of the people, who asked not to be named because the matter isn’t public.